The present invention is directed to nucleic acid and amino acid sequences and constructs, and methods related thereto.
Fatty acids are organic acids having a hydrocarbon chain of from about 4 to 24 carbons. Many different kinds of fatty acids are known which differ from each other in chain length, and in the presence, number and position of double bonds. In cells, fatty acids typically exist in covalently bound forms, the carboxyl portion being referred to as a fatty acyl group. The chain length and degree of saturation of these molecules is often depicted by the formula CX:Y, where xe2x80x9cXxe2x80x9d indicates number of carbons and xe2x80x9cYxe2x80x9d indicates number of double bands. As the carbon chain of fatty acyl molecules always contains an even number of carbons, the formula xe2x80x9cC2Xxe2x80x9d may also be used to represent carbon chain length.
Fatty acyl groups are major components of many lipids, and their long, non-polar hydrocarbon chain is responsible for the water-insoluble nature of these lipid molecules. The type of covalent linkage of the fatty acyl group to other factors can vary. For example, in biosynthetic reactions they may be covalently bound via a thioester linkage to an acyl carrier protein (ACP) or to CoenzymeA (CoA), depending on the particular enzymatic reaction. In waxes, fatty acyl groups are linked to fatty alcohols via an ester linkage, and triacylglycerols have three fatty acyl groups linked to a glycerol molecule via an ester linkage.
The fatty acid composition of an oil determines its physical and chemical properties, and thus its uses. Plants, especially plant species which synthesize large amounts of oils in plant seeds, are an important source of oils both for edible and industrial uses.
A wide range of novel vegetable oils compositions and/or improved means to obtain or manipulate fatty acid compositions, from biosynthetic or natural plant sources, are needed for a variety of intended uses. Plant breeding, even with mutagenesis, cannot meet this need and provide for the introduction of any oil traits which are outside of the target plant""s gene pool.
Various oils compositions are now in demand. For example, edible oil sources containing the minimum possible amounts of saturates, palmitate (C16:0) and stearate (C18:0) saturated fatty acids, are desired for dietary reasons and alternatives to current sources of highly saturated oil products, such as tropical oils, are also needed. Generating a spread of C4, C6 and C8 short chain 3-keto fatty acids could become a key improvement in polyhydroxybutyrate (PHB)-based biodegradable plastics made in bacteria and plants. Medium-chain fatty acids have special importance in the detergent and lubricant industries or in the formulation of edible oils with reduced caloric value or other health benefits. See for example, U.S. Pat. No. 4,863,753 and Barch, A. C. and Babayan, V. K., Am. J. Clin. Nat. (1982) 36:950-962. Longer chain fatty acids may have certain other utilities, i.e., C16 and C18 have particular uses in margarine and other solid oil-based products and very long chain fatty acids also have specialized uses, i.e., C22 is used to make peanut butter smoother. As such, a ready source of a variety of fatty acid lengths, including storage lipids which have incorporated differing chain length fatty acids in desired ratios, are desired for a variety of industrial and food use fields. Improved yield of current oilseed crops and the development of novel plant fatty acid compositions and oils products are also needed. Examples of novel plant fatty acid and oils products include fatty alcohols, epoxy fatty acids (e.g., biodegradable paint thinner), long chain liquid wax (e.g., jojoba oil substitute), hydroxylated fatty acids (motor lubricants) or cyclopropanated fatty acids (motor lubricants).
There is a need for improved means to obtain or manipulate compositions fatty acids from biosynthetic or natural plant sources. For example, novel oil products, improved sources of synthetic triacylglycerols (triglycerides), alternative sources of commercial oils, such as tropical oils (i.e., palm kernel and coconut oils), and plant oils found in trace amounts from natural sources are desired for a variety of industrial and food uses. Or, the ability to increase total oil production in plants may provide for novel applications of seed oils for use in human and animal nutrition.
The present invention is directed to fatty acid xcex2-oxidation polynucleotides, and in particular to acyl-CoA oxidase (ACOX) polynucleotides. The present invention further provides 3-ketoacyl-CoA thiolase (thiolase) polynucleotides. The polynucleotides of the present invention include those derived from plant sources.
One aspect of the present invention relates to oligonucleotides which include partial or complete ACOX or thiolase encoding sequences.
It is also an aspect of the present invention to provide recombinant DNA constructs which can be used for transcription or transcription and translation (expression) of ACOX and/or thiolase. In particular, constructs are provided which are capable of transcription or transcription and translation in host cells. Particularly preferred constructs are those capable of suppression of endogenous host cell ACOX and/or thiolase.
In another aspect of the present invention, methods are provided for production of ACOX and or thiolase in a host cell or progeny thereof. In particular, host cells are transformed or transfected with a DNA construct which can be used for transcription or transcription and translation of ACOX and/or thiolase. The recombinant cells which contain ACOX and/or thiolase are also part of the present invention.
In a further aspect, the present invention relates to methods of using polynucleotide and polypeptide sequences to modify the fatty acid content as well as composition, particularly in seed tissue of oilseed crops. Plant cells having such a modified fatty acid content are also contemplated herein.
In yet a further aspect, the present invention relates to methods of using polynucleotide and polypeptide sequences to inhibit or delay the germination of seeds.
The modified plants, seeds and oils obtained by the expression of the plant ACOX proteins are also considered part of the invention.